Instrument for drawing circles.



1. H. McMURRAY.

INSTRUMENT FOR DRAWING CIRCLES.

APPLICATION FILED OCT- 22, 1914.

1,201,209. Patented Oct. 10, 1916.

2 SHEETS-SHEET I.

Due/1751' I. H. McMURRAY.

INSTRUMENT FOR DRAWING CIRCLES.

APPLICATION FILED OCT- 22, 19M.

Patented Oct; 10, 1916.

2 SHEETS-SHEET 2.

barren s'rarns PATENT orrrlcn. 4'

JOHN H. MOMURRAY, OF SOHENECTADY, NEW YORK, ASSIGNOR OF ONE-HALF 'IOJOHN T. GORMAN, OF COI-IOES, NEW YORK.

INSTRUMENT FOR DRAWING CIRCLES.

Application filed October 22,

To all whom it may concern:

Be it known that I, JOHN H. MGMURRAY, a citizen of the United States,residing at Schenectady, in the county of Schenectady and State of NewYork, have invented new and useful Improvements in Instruments forDrawing Circles, of which the following is a specification.

My present invention relates to instruments for drawing circles or arcsand is an improvement upon instruments of the class shown and describedin my prior Patents 951,255 and 1,005,992, granted March 8, 1910, andOctober 17, 1911 respectively.

I The primary objects of the invention are, to provide simple andimproved means for operating the scribing point, to provide improvedmeans whereby the scribing point is caused to bear upon the surfaceduring the scribing operation and to lift or disengage therefrom whenthe scribing of the circle or a desired arc thereof has been completed,to provide means whereby the pressure of the scribing pointupon thesurface may be regulated, and to provide means whereby the scribingpoint will operate with uniform pressure although the'operating meansmay be out of perpendicular to the surface upon which the circle or anarc thereof is to be drawn.

To these and other ends, the invention consists in certain improvements,combinations and arrangements of parts, all as will be hereinafter morefully described, the features of novelty being pointed out particularlyin the claims at the end of the specification.

In the accompanying drawings, Figure 1 is a perspective view of aninstrument constructed in accordance with the present invention. Fig. 2represents a central, longitudinal section of the instrument with theparts in readiness for the scribing operation. Fig. 3 represents acentral, longitudinal section through the instrument in a planeperpendicular to the section represented by Fig. 2 and showing the partsin the positions they occupy after the scribing operation has beencompleted. Fig. 4; represents a transverse section on the line 44: ofFig. 2. Figs. 5 and 6 are detail perspective views of the socket and thebeam holding-f-raine respectively. Fig; 7 represents a Specification ofLetters Patent.

Patented Oct. 10, 1916. 1914. Serial No. 868,086.

transverse section on an enlarged scale and takeno-n the line 77 of Fig.2. Fig. 8 represents a section on the line 8-8 of Fig. 2; and Fig. 9represents a section on the line 99 of Fig. 2.

Similar parts are designated by the same reference characters in theseveral views.

The present invention. is particularly applicable to instruments fordrawing circles of the type shown and described fully in my priorpatents above mentioned, and the im-v provements are shown and will behereinafter described as applied to an instrument of that type. It willbe understood, however, that the invention is not restricted toinstruments of that particular type and also that the invention is notrestricted to the particular construction shown, as equivalentconstructions within the scope of the claims are contemplated.

In the present instance, the device embodies a base 1 adapted to bearupon the surface on which the circle or an are thereof is to be drawn.As shown, it embodies a rim 2 having a ring .3 of rubber secured theretoand adapted to bear frictionally upon the surface on which the circle isto be scribed. As the base of the instrument is to be placed at thecenter of the circle or are to be drawn, it'is preferable to provide anindex or pointer i which is in alinement with the center of theinstrument and is adapted to be placed at the center of the circle orarc. On the base is mounted a socket member 5 which receives the memberor beam which carries the scribing point. In the present instance, thissocket member istubular, it having a bottom 6 which is pivotallyconnected to the base 1. struction shown, the indeX or pointer 4 isutilized as a pivot connecting the base to the socket. A pair of pivotarms 6 project from one side of the socket member and the latter isformed with openings 7 and 8 in diametrically opposite sides thereof toreceive a beam carrying member 9. The latter is pivoted at one end tothe laterally projecting arms 6 which are located at one side of thecenter of the instrument. In order to enable the pivotal center of themember In the con-' 9 to be set at different distances from thecenterofthe instrument and thereby vary the pressure of the scribingpoint as Will hereafter appear, the arms 6 are formed with a pluralityof spaced apertures 10 to receive the pivot pins 11. The member 9 has agenerally rectangular cross section and is hollow.

One end 12 of the member has an aperture 13, and the opposite end ofsaid member 1s provided with a socket 14c whlch contains an aperture 15corresponding to the aperture 13. The beam 16 or arm which carries thescribing point is adapted to be inserted in the apertures 15 and 13 andis slidable long1- tudinally in these apertures, in order that thedistance of the scribing point from the center of the instrument may bevaried in accordance with variations in the radii of the circles or arcsto be drawn. In the construction shown, the beam 16 is substantiallyround in cross section, and in order to avoid turning of the beam in thesocket 141:, the latter is provided with a key 17 which is adapted toslide longitudinally in a keyway 18 formed in the beam. Preferably, thesocket 1a is swiveled on the frame of the member 9 in order that thebeam 16 may be swung into a position at one side or in parallelism withthe body of the instrument when the same is not in use. In theconstruction shown, the socket is mounted on a frame 9 by the pivot 17at one side and a screw 18 at the opposite side, the screw 18 alsoserving as a clamp to secure the beam 16 in different adjustedpositions. The outer end of the beam is provided with means for holdingan appropriate scribing point. In

the construction shown, it is provided with,

a clip or holder for a stick of chalk, the clip or holder embodying apair of segmental jaws 19 and 20 which are adapted to receive the chalkbetween them, and these jaws are carried by the resilient or springyarms 21 and 22 which proceed from the outer end to the beam. A ring 23is movable longitudinally along the arms 21 and 22 and thereby operatesto force the jaws together to clamp the chalk or to release the jaws andpermit opening thereof. The opposite end of the beam which can be ahollow metal tube is preferably filled with suitable material to form acounterbalance 24 to compensate for the weight of the chalk and itsholder.

A tubular casing or sleeve 25 is fitted in the upper end of the socketmember 5 in such a manner that it may have a limited and axial movementrelatively to the socket member and may also have a tilting motionrelatively thereto. In the construction shown, the socket member isformed with longitudinal slots 26, and the lower end of the casing orsleeve 25 carries pins and screws 27 arranged to operate in the slots 26to permit the movements just described. The lower end of the casing orsleeve 25 is also surrounded by a sleeve 28 which expanded outwardlyfrom the sleeve or casing 25 and fit into an interior annular groove 30in the sleeve 28. The interior of the sleeve 28 is preferably formedwith an incline 31 which will operate to contract the tongues 29 as thesleeve 28 is moved into position, these tongues thereupon expandingwithin the groove 30 and thus retaining the sleeve .in proper position.The casing or sleeve 25 contains a spiral member 32 which constitutespart of the means for operating the scribing point. I referably, thisspiral member is composed of a strip of metal which is fiat in crosssection and is twisted on its longitudinal axis. As shown, the lower endof the spiral member is fixed to the casing or sleeve 25 by a stem 33 onthe lower end thereof which is threaded or otherwise secured to a part34: which latter is secured immovably to the bottom of the casing orsleeve 25. The upper end of the spiral member 32 is secured to afollower 35 which latter is adapted to slide freely within a hollow ortubular plunger 36, the latter telescoping or moving longitudinallywithin the casing or sleeve 25. The plunger 36 has a handle or knob 37at its outer or upper end for operating it and is provided at its loweror inner end with a clutch which operatively connects the plunger 36 tothe casing or sleeve 25 and its related parts when the plunger is forcedinwardly and which permits withdrawal of the plunger without causingrelative rotation between the casing or sleeve 25 and the plunger. Inthe construction shown, a clutch member 38 is fixed l within the plunger36 and has ratchet teeth 37 thereon adapted to cooperate with companionratchet teeth formed on the cooperating clutch member 38, the latterbeing revolubly mounted within the plunger 36 and is yieldingly held incooperative relation with the clutch member 38 by a compression spring39. The movable clutch member 38 is provided with a pair of rollers 40which are adapted to travel along the fiat sides of the spiral member 32as the plunger is operated, the ratchet teeth of the clutch membersbeing then engaged and as the handle 37 is held from turning during theworking stroke of the plunger, the rollers 40 will maintain their aXesin a fixed direction, and the spiral member 32 passing be tween them tobe rotated, and the rotation of the spiral member will be transmitted tothe socket member 5 and thence through the frame 9 to the beam causingthe scribing point to rotate about the pointer 4' as an aXis.

According to the present invention, the scribing point is caused to bearwith the desired degree of pressure upon the surface on which the circleor are thereof is to be drawn and means is also provided for tilting ordisengaging the scribing point from such surface when. the circle or thedesired arc thereof has been drawn. In the construction shown, acompression spring 42 is fitted in the lower portion of the socketmember 5 and bears upwardly or against the. under side of the member 9tending to swing the same upwardly about its axis and to thereby lift ordisengage the scribing point or chalk. Means is also provided forexerting a yielding pressure on the member 9 tending to lower it andthereby engage the scribing point with the surface. As shown, a springseat l3 is placed below the part 34 and has a stem 4A which is centeredin a socket 45 formed in the stem 33 and a bow spring i6 is interposedbetween the spring seat as and the part 3th. The spring seat 43 isadapted to bear downwardly on the beam carrying member 9. In order tovary the degree of such pressure, a movable fulcrum l7 is provided whichis adapted to be ad justed in a direction toward or from the pivotalcenter of the beam carrying member by a screw 48 which is journaled in apair of lugs 49 and 50 which may be struck up from the top of the beamcarrying memher 9. This provides a close adjustment for the pressure ofthe scribing point and a greater degree of adjustment can be obtained byshifting the pivotal center of the beam carrying frame. In order toavoid squeaking or vibration of the scribing point or chalk during thescribing operation, the same is inclined as shown, whereby the chalk orscribing point has a dragging movement over the board or surface onwhich the circle is to be drawn.

In operation, the instrument is applied to a blackboard or other surfaceby placing the index or pointer 4: at the center of the circle or areand then the operator presses the sleeve 28 toward the board or surface,thus operating to force the sleeve or casing into the socket member 5and thus pro ducing pressure between the spring seat 43 and the fulcruml7 to a degree sufficient to overcome the effect of the spring 42 and tomove the chalk or scribing point into engagement with the board orsurface. The plunger 36 is then forced inwardly and the member 32 andits cooperating parts convert the longitudinal movement of the plungerinto rotary motion to swing the beam and the scribing point about thepointer 4 of vthe center, thus scribing a circle or any desired arc ofthe circle. incident to the inward thrust of the plunger serves tomaintain a pressure upon the spring seat 43 and the latter operatesyieldingly and uniformly to press the chalk or scribing point upon thesurface. When the circle or the .desired-- arc thereof has been Part ofthe force completed, the pressure of the plunger is relicved and thespring 42 will then act to lift or disengage the chalk or scribing pointfrom the board or surface.

Having fully described my invention, I claim v 1. An instrument fordrawing circles comprising a base, a beam rotatable thereon and carryinga scribing point, a member movable axially of the beam, means forconverting the axial movement of said member into rotary movement torotate the beam, and means operative by pressure incident to such axialmovement of said member to press the scribing point upon the surface onwhich the circle is to be drawn.

2. An instrument for drawing circles comprising a base, a beam rotatablethereon and carrying a scribing point, an operating member movable inthe direction of the axis of rotation of the beam, means operative bysuch movement of said member to rotate the beam, means also operative bysuch movement of said member to press the scribing point upon thesurface on which the circle is to be drawn, and means for disengagingthe scribing point from said surface.

3. An instrument for drawing circles comprising a base, a beam rotatablewith respect thereto and carrying a scribing point, an operating membermovable in the direction of the axis of rotation of said beam, meansoperative by said member to rotate the beam, means also operative by theaxial movement of said member to press the scribing point upon thesurface on which the circle is to be drawn, and means acting inopposition to the means first mentioned for disengaging the scribingpoint from said surface.

4. An instrument for drawing circles comprising a base, a beam rotatablethereon and carrying a scribing point, means acting yieldingly to holdthe scribing point in disengaged relation to the surface on which thecircle is to be drawn, and means movable in the direction of the axis ofrotation of the beam and operative by pressure applied thereto to rotatethe beam and capable of overcoming the force of said yieldingly actingmeans to press the scribing point upon.

said surface.

5. An instrument for drawing circles, comprising a base, a beamrotatable thereon and carrying a scribing point, means acting yieldinglyto hold the scribing point, in disengaged relation to the surface onwhich the circle is to be drawn, a member movable toward the, beam bypressure applied thereto, means operative by the pressure applied tosaid member to rotate the beam, and means operative by pressure appliedto said member to press the scribing point upon said 'sllrfae- I r 6. Aninstrument for drawing circles comprising a base, a beam rotatablethereon and carrying a scribing point in disengaged relation to thesurface on which the circle is to be drawn, a device for initiallyengaging the scribing point with said surface, and means movable towardthe beam and operative by pressure appliedthereto to rotate the beam andto maintain the scribing point in engagement with said surface.

7. An instrument for drawing circles comprising a base, a beam rotatablethereon and carrying a scribing point, means acting yieldingly to holdthe scribing point in disengaged relation to the surface on which thecircle is to be drawn, a member movable by the application of forcethereto in a direction toward the base, means for converting suchmovement of said member into motion to rotate the beam, and meansoperative by the pressure applied to said menr her to yieldingly pressthe scribing point upon said surface.

8. An instrument for drawing circles comprising a base, a beam rotatablyand tiltably mounted thereon and carrying a scribing point, means actingyieldably to tilt the beam and hold the scribing point in disengagedrelation to the surface upon which the circle is to be drawn, and meansincluding a plunger movable toward the base and operatively connected tothe beam to rotate the latter and also including means acting on thebeam to maintain the scribing point in engagement with said surface inopposition to said yieldingly acting means.

9. An instrument for drawing circles comprising a base, a beam rotatablyand tiltably mounted thereon and carrying a scribing point, means actingyieldably to tilt the beam and hold the scribing point in disengagedrelation to the surface upon which the circle is to be drawn, and meansincluding a plunger movable toward the base and oper-atively connectedto the beam to rotate the latter and also including a pressuretransmitting member acting on the beam in opposition to said yieldinglyacting means to maintain the scribing point in engagement with saidsurface and means for adjusting said pressure transmitting member tovary the degree of pressure so exerted by the scribing point on saidsurface.

10. An instrument for drawing circles comprising a centering base, asocket rotatable thereon, a beam carrying a scribing point, a frameconnected to the beam and tiltably mounted on said socket, a spring inthe socket acting on said frame to yieldingly hold the scribing point indisengaged relation to the surface on which the circle is to be drawn,and means including a plunger movable toward the base and operated torotate the beam and also to bear on said frame in opposition to saidspring and there- I by maintain the scribing point in engagement withsaid surface.

11. An instrument for drawing circles comprising a centering base, asocket rotatable thereon, a beam carrying a scribing point, a frameconnected to the beam and tiltably mounted on said socket, a spring inthe socket acting on said frame to yieldingly hold the scribing point indisengaged relation to the surface on which the circle is to be drawn,and means including a plunger movable toward the base and operated torotate the beam and also to bear on said frame in opposition to saidspring and thereby maintain the scribing point in engagement with saidsurface and carried by and adjustable relatively to said frame forvarying the effective force of pressure of the plunger on said frame.

12. An instrument for drawing circles comprising a centering base, asocket rotatable thereon, a beam carrying a scribing point, a frameconnected to the beam and tiltably mounted on said socket, a spring inthe socket acting on said frame to yieldingly hold the scribing point indisengaged relation to the surface on which the circle is to be drawn,and means including a plungcr movable toward the base and operated torotate the beam and also to bear on said frame in opposition to saidspring and thereby maintain the scribing point in engage ment with saidsurface, the axis on which said frame tilts being adjustable to vary thepressure of the scribing point on said surface.

13. An instrument for drawing a circle comprising a centering base, asocket rotatable thereon, a. beam carrying a scribing point, a frameconnected to the beam and tiltably mounted on said socket, a spring inthe socket acting on said frame to yield-- ingly hold the scribing pointin disengaged relation to the surface on which the circle is to bedrawn, and means including a plunger movable toward the base andoperated to rotate the beam and also including a fulcrum on said framearranged to receive pressure from said plunger in opposition to saidspring and thereby maintain the scribing point in engagement with saidsurface, said fulcrum being shiftable relatively to said frame to varythe point of application of pressure by the plunger on said frame and tothereby vary the pressure of the scribing point on said surface.

14. An instrument for drawing circles, the combination of a centeringbase, a socket rotatable thereon, a beam carrying a scribing point, aframe tiltably mounted on said socket and cooperative with the beam, aspring acting on said frame to yieldingly hold the scribing point indisengaged relation to the surface on which the circle is to be drawn, asleeve movable axially of said socket, a plunger reciprocable in saidsleeve toward the base, means for transmitting the thrust of saidplunger through said sleeve to said frame'to maintain the scribing pointin engagement with said surface, and means for connecting the movementof said plunger into rotatable movement of the beam.

15. An instrument for drawing circles comprising a centering base, abeam rotatable thereon and carrying a scribing point, and meansincluding a plunger movable toward the base for rotating the beam andalso including means for maintaining the scribing point in engagementwith the sur face on which the circle is to be drawn by pressuretransmitted thereto incident to the movement of the plunger toward thebase, said last mentioned means being capable of adjustment from theaxis of rotation of the beam.

16. An instrument fordrawing circles comprising a centering base, a beamrotatable thereon and carrying a scribing point, and means for rotatingthe beam embodying a plunger movable toward the base, a spiral memberflat in cross section and operatively connected to the beam, and rollerscarried by the plunger and cooperative with the fiat sides of saidspiral member.

In testimony whereof I have hereunto set any hand in presence of twosubscribing Witnesses.

JOHN H. MQMURRAY. lVitnesses WVALTER D. GooDALE, FRANK E. GOODALE.

copies of this patent may be obtained for five cents each, by addressingthe commissioner of latenti,

Washington, D. G. I

